A continuing challenge in chemical processes is increasing product yield and reducing costs associated with such processes. An example of one such process is the Fischer-Tropsch process, which is commonly facilitated by a catalyst.
In the Fischer-Tropsch process, a feed containing carbon monoxide and hydrogen is typically contacted with a catalyst in a reactor to form a range of hydrocarbons including gases, liquids and waxes. Catalysts desirably have the function of increasing the rate of a reaction without being consumed by the reaction. The catalyst is typically included within a catalyst support.
Fischer-Tropsch catalysts typically include a catalytic metal and are usually included in a catalyst support. The catalyst support is typically a porous material that provides mechanical strength and a high surface area, in which the active metal and promoter(s) can be deposited.
A catalyst support material is desirably stable. One example of a catalyst support is gamma alumina supports, which are desirable due to their lower reactivity than other comparable catalyst supports. Despite the tendency of gamma-alumina to be stable at atmospheric conditions, conventional Fischer-Tropsch catalyst supports such as gamma-alumina is known to exhibit a tendency to instability under hydrothermal conditions. For example, gamma-alumina undergoes an increase in average pore size and an accompanying decrease in surface area after hydrothermal treatment in the temperature range of about 150-300° C. In other words, gamma alumina supports are susceptible to water poisoning. Such a transformation would be undesirable in a catalyst. However, similar hydrothermal conditions occur, for example, in the Fischer-Tropsch process. In particular, in a Fischer-Tropsch process, water is produced during the Fischer-Tropsch reaction. The presence of water together with the elevated temperatures conventionally employed in the Fischer-Tropsch process create conditions in which hydrothermal stability, which is stability at elevated temperatures in the presence of water, is desirable. Thus, Fischer-Tropsch catalysts using gamma-alumina supports are known to exhibit a tendency to hydrothermal instability under Fischer-Tropsch operating conditions. This instability tends to cause a decrease in performance of gamma-alumina supported catalysts.
Finely divided supported catalysts used in fluidized or slurry systems have been known to attrite and deactivate, which causes longevity concerns and product separation issues due to fines formation. The attrition and the deactivation may be due in part to hydrothermal degradation by high pressure and temperature steam from water formed in the reactor. Particularly, the high pressure and temperature steam may promote rehydration of the catalyst support, such as in the case of an alumina support to boehmite and/or gibbsite phases causing a change in the chemical structure and leading to structural instability.
More recently, enhanced Fischer-Tropsch catalyst supports having improved hydrothermal stability have been developed such as those taught in U.S. Pat. No. 7,449,496, titled, “Stabilized Boehmite-Derived Catalyst Supports, Catalysts, Methods of Making and Using,” filed Oct. 19, 2007, referred to therein as stabilized catalyst supports and stabilized aluminum oxide structures.
However, the use of these enhanced catalyst supports have not been successfully extended to other chemical processes outside of the Fischer-Tropsch process.